solar aperture size?

[nickdud]

i am building a solar filter for my scope using solar film and a couple of new drain pipe ends(more later), i have up to 100mm diameter to play with but was wondering if i need a larger or smaller diameter aperture for best solar results?(sunspots/dark side of rolling clouds/oncoming rain and hurricanes,etc)

any advice please peeps?

(scope is a 600mm,st120)

cheers:D

[Uhwaz]

MAKE ABSOLUTELY SURE you cover whole aperture ( and it sits on scope tight ) and theres no pin holes etc ... small hole in your filter and in better case you only loose eye !!!

[nephilim]

As Uhwaz says, always check for any wear or pinholes before EVERY session, as long as the 'sleeve' (drainpipe in your case, plantpot in mine ) fits nice & snug over the scope it should be fine, I also put a couple of pieces of masking tape on from sleeve to scope to make sure it wont slip or fall off. btw & i dont mean to be patronising but never leave the scope pointed toward the sun unattended even for a second (even with the filter on) as it only takes a split second for an inexperienced family member/friend to have a quick look & do permenant damage to their eye. On a more positive note, the first time I saw the sun in its natural white light I was blown away, its a fantastic sight and one you'll keep going back to time after time.

Steve

[Moonshane]

as long as you make a filter that cannot come off and cannot let light lean in then solar observing is very safe with the Baader film.

to answer your question, I'd use the full aperture you can so the 100mm. with my 6" f11 dob, I use a full aperture filter which works superbly.

[Steve Ward]

I use the same scope for my Solar imaging , go for full aperture.

A really easy way of making a filter is to use an "embroidery ring" and 3 small bolts for securing .

[Merlin]

In case you don't already know it, avoid stretching the film. Also, there's a layer of clear protective film on one side of the coated film that has to be peeled off.

[nickdud]

cool, thanks folks, i still have a few bits to add to my drain to fully secure it to scope but the base is almost there now.

and thanks again for all the warnings, i will be double sure to double check, i opted for film over a herschel wedge after reading here about someone who almost toasted his scope do i can understand how hot it gets.

there is some good stuff on youtube about a bloke in the us making lenses with polythene sheet and water and watching him melt metal is pretty scarey stuff

[JamesF]

I would definitely use the full aperture. I read somewhere recently that ideally you want up to 120mm to be able to pick out some of the finer detail, though I'd have to admit that I have no idea how that figure was derived.

James

[Peter Drew]

Probably the old rule of thumb 4.56 divided by aperture to give theoretical resolution in arcseconds. The finest details visible in white light are around 1 arcsecond, however daytime sunny seeing is rarely that good.

[steveb1977]

In case you don't already know it, avoid stretching the film. Also, there's a layer of clear protective film on one side of the coated film that has to be peeled off.

I've used Baader for years and i didn't know this. Will have to check my filter out!

[Moonshane]

another one which I fell foul of was sticking the clear (disposable) film into my filter. I had to cut it out again and redo it.

[Moonshane]

Probably the old rule of thumb 4.56 divided by aperture to give theoretical resolution in arcseconds. The finest details visible in white light are around 1 arcsecond, however daytime sunny seeing is rarely that good.

thanks Peter - didn't know this.

a quick google confirms :

θ = 4.56/D, with D in inches and θ in arcseconds

(I googled it to confirm whether D was inches or mm not to check what you said).

I cannot see my 16" dob every resolving 0.285 arcseconds either

[JamesF]

That makes a lot of sense then

James